Archived posting to the Leica Users Group, 1999/01/27

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Subject: Re: [Leica] Re: glass or plastic
From: "Dan Post" <>
Date: Wed, 27 Jan 1999 15:26:24 -0500

 I have been reading this thread with interest and I would like to pose a
question- maybe Erwin might have some info to give insight to the question
I switched to plastic spectacle lenses because the refraction I require
makes the prescription so heavy in glass, that for years I hated wearing
glasses. With the advent of high refraction plastics, I have a very light
pair of glasses, and don't often wear my contacts because the specs are so
comforatble now.
In the same vein, it seems to me that with the malleability of plastic, the
lenses using them would be stury yet light. I also realise that aspherical
elements, while not necessary, are like the  Programmed Array Logic devices
in computers. The single PAL can replace many energy consuming chips, with
one- and the aspherical element can lessen the element count. So, what is
the disadvantage of a lens with fewer elements and air-to-glass surfaces,
and lighter?
Of course, the plastic spectacles get scratched, and I would assume that in
a camera lens, that the plastic elements would be interio, but it seems to
me that there would be not real disadvantage.
It makes me recall the experience we had at the police department when the
detectives were issued Glocks; there was concern over the plastic resin
slide. They were afraid the plastic would not stand up, plastic melts,
plastic is inferior. Actually, the lead in the cartridges would melt before
the plastic, and with impacts tests, the Glock , singularly, survived a
multistory fall from a building, where are the more traditionally made
weapons didn't.
So, what's wrong with plastics?